Which one is correct?
I am enthusiastic about gaining knowledge of medicine particularly in X and Y techniques.
I am enthusiastic about gaining knowledge of medicine particularly about X and Y techniques.
Many thanks.
[native:Australian]
I would use "in".
You could also say: "I am enthusiastic about gaining a knowledge of medicine, in particular, X and Y techniques."
I can't tell you with certainty why this is the case, sorry. Just sounds right to me. I suspect that you are interested "in the technique" rather than about it. That is, that you wish to learn how to become a practitioner of the technique rather than learning attributes of it (which might be who performs it, how long it has been performed, who pioneered it, and so on).
Hope this helps.
"In" is better, but the whole sentence is a bit awkward.
"I am looking forward to expanding my knowledge of medicine, particularly regarding the techniques of X and Y," sounds more natural.